1. Field of the Invention
The invention relates to a geometric construction system, more particularly to a geometric construction system having flat panels that can releasably engage each other through a connecting unit.
2. Description of the Related Art
FIG. 1 illustrates a conventional geometric-construction system disclosed in U.S. Pat. No. 4,055,019. The geometric construction system includes flat panels and connecting units 1 provided respectively on side edges of each of the flat panels for edgewise interengagement among the flat panels. Each of the connecting units 1 includes first and second engaging parts 13, 14 and first and second inserting spaces 11, 12 that are disposed at two opposite sides of the second engaging part 14. The first and second engaging parts 13, 14 are spaced apart from each other by the first inserting space 11. The first engaging part 13 is formed with a recess 151. The second engaging part 14 is formed with a protrusion 181. Upon edgewise interengagement between two of the flat panels, the second engaging part 14 on one of the two flat panels is received in the first inserting space 11, the protrusion 181 of the second engaging part 14 on said one of the two flat panels engages the recess 151 in the first engaging part 13 on the other of the flat panels, the first engaging part 13 on said one of the flat panels is received in the second inserting space 12, and the recess 151 in the first engaging part 13 on said one of the flat panels receives the protrusion 181 of the second engaging part 14 on the other of the flat panels. A first slit 141 is formed in the second engaging part 14. A second slit 143 is formed in each of the side edges of each of the flat panels, and cooperates with the first slit 141 to form the second engaging part 14 with a resilient end portion 142 that confines an end of the first inserting space 11 so as to facilitate insertion of the second engaging part 14 on said one of the flat panels into the first inserting space 11.
FIGS. 2 and 3 illustrate other conventional geometric construction systems that differ from the previous geometric construction system shown in FIG. 1 in the shapes and depths of the slits 141 (143).
The aforesaid conventional geometric construction systems suffer from a common drawback in that connection between two flat panels through engagement between the protrusion 181 and the recess 151 is relatively poor, which can cause the engaged flat panels to disconnect from each other during construction or playing with the flat panels. In addition, the shape and size of the resilient end portion 142 of the second engaging part 14 of the aforesaid conventional geometric construction systems, which is formed through formation of the slits 141 (143), are required to have a relatively high precision so as to provide the resilient end portion 142 with adequate flexibility for facilitating insertion of the second engaging part 14 into the first inserting space 11 and so as to provide suitable resilient forces for engagement between the protrusion 181 and the recess 151.